The present invention generally relates to a document shredder for cutting documents to be disposed of (referred to as paper sheets to be shredded hereinafter) into small pieces or narrow strips, and more particularly, to an automatic paper feeder for automatically feeding paper sheets to be shredded in a document shredder.
Conventionally, as shown in FIG. 7, an automatic paper feeder generally includes a paper feeding table T for placing thereon, a stack of many paper sheets P to be shredded, a feeding roller F disposed at a small distance k from a leading edge p of the paper sheet P for feeding said paper sheet P to be shredded, to a set of shredding blades B, a driving device M for driving the feeding roller F for rotation, a pivotal plate Ta for the feeding table T, a pressure spring S for urging said pivotal plate Ta upwardly, a transport roller R, an endless transport belt V passed around said rollers F and R, and a guide path G for guiding the paper sheets P towards the shredding blades B.
In the automatic feeder for the document shredder as described above, it is normally required to cut the paper sheets P to be shredded still more positively and quickly. Although it is essential to increase revolutions of the shredding blades B in order to raise the shredding speed, excessive increase of the revolutions undesirably increases a load to be applied to the shredding blades B, and requires a large-sized driving source or motor for rotating the shredding blades 2. Moreover the shredding blades B are also required to have a sufficient strength to withstand such shredding load, thus inviting a cost increase for satisfying such requirements.
Furthermore, since the feeding roller F is arranged to feed the large number of paper sheets, one sheet by one sheet at its upper or under surface, it is required to have a separating effect. In order to improve such separating effect, the feeding roller F is disposed at a position retreated from the leading edge p of the paper sheet P to be shredded by a preliminarily overlapping length k.
As a result, the paper sheets P are fed in a state of two layers at the forward end portion in which the trailing edge of a preceding paper sheet P.sub.1 overlaps the leading edge of a successive paper sheet P.sub.2 by the preliminarily overlapping length k as shown in FIG. 6. It is to be noted here, however, that, if the length k is increased, small-sized paper sheets to be shredded can not be fed.
Accordingly, under the specified conditions, increasing the degree of overlapping of the paper sheets P without increasing the length k will provide means for increasing in shredding speed.